Process for the dehydrogenation of a tetrahydroanthraquinone to an anthraquinone



United States Patent 7 Claims. (51. 23-207 This invention relates to a process for the dehydrogenation of a tetrahydroanthraquinone to the corresponding anthraquinone. More particularly it relates to a process for the dehydrogenation of a tetrahydroanthraquinone formed during the course of the production of hydrogen peroxide by a cyclic operation involving the reduction of an anthraquinone and the oxidation of the resultant anthrahydroquinone.

The inventors proposed, in Japanese patent application Sho 35/ 42,347, a process of the dehydrogenation of tetrahydroanthraquinones to anthraquinones, which comprises contacting tetrahydroanthraquinones with any one compound selected from alumina, magnesia, and aluminamagnesia in spinel form, or a metal which is known to foster hydrogenation in general such as palladium or nickel supported on one of the above mentioned oxides, or a mixture consisting of said substances, and a metal oxide selected from the oxides of copper, silver, lead, mercury or manganese at a reaction temperature from 80300 C. in an environment of an inert gas. The present invention is practised with greater ease, compared to said process. Another process is described in US. Patent No. 2,948,739 for the dehydrogenation of an alkylated tetrahydroanthraquinone, in which the tetrahydroanthraquinone formed in the production of hydrogen peroxide by an anthraquinone process, is dissolved in acetophenone and dehydrogenated in the presence of palladium or Raney nickel supported on activated carbon at a temperature above 150 C.

According to this prior art process the one stage conversion of an alkylated tetrahydroanthraquinone to the corresponding anthraquinones is kept at around 30%, partly because the conversion does not exceed 40% owing to the equilibrium present, and partly because the loss of the alkylated tetrahydroanthraquinone is accelerated when the conversion draws near the equilibrium, said loss being possible to reach over 30%.

The solution subjected to dehydrogenation is cooled after the first stage of dehydrogenation, oxidized with oxygen and submitted to the second stage of dehydrogenation. Thus the total conversion of 70-80% is attained after repeating three times the dehydrogenation process.

With the aim of breaking the equilibrium, which exists when a hydrogenation catalyst alone is employed, to complete the reaction and obtain a quantitative yield, the inventors proposed the aforementioned process.

It has now been found according to this invention that the equilibrium is broken by removing from the reaction system the hydrogen which in turn has been removed from the tetrahydroanthraquinone. This is accomplished by introducing substances which easily react with hydrogen such as olefines into the reaction system, whereby the hydrogen emanating from the tetrahydroanthraquinone hydrogenates the olefines.

The present invention is practised in the following way. A substance selected from alumina, magnesia, aluminamagnesia in spinel form, active carbon, or a carbonate of a metal selected from Group I or II of the Periodic Table, or a mixture of the above mentioned substances, and a metal which is known to foster hydrogenation in general such as palladium, platinum or nickel are added to a solution comprising a tetrahydroanthraquinone. The solution is then contacted with an organic compound having at least one unsaturated bond, at a temperature exceeding C. to lead the dehydrogenation to completion with a quantitative yield.

In the instance where an unsaturated compound is not introduced into the system and the reaction is carried out in an environment of an inert gas such as nitrogen, the conversion of the tetrahydroanthraquinone reaches only 55% and the total anthraquinone recovery is reduced to 70%.

The present invention is characteristic in that the reaction is completed by a simple one stage operation with a quantitative yield.

Another characteristic of the invention is that the working solution, employed in the production of hydrogen peroxide by the so-called anthraquinone process, which con sists of a solution comprising an anthraquinone dissolved in solvents such a hydrocarbons, aliphatic alcohols, phos-- phoric acid esters or acetophenone may be submitted to the dehydrogenation process without any pre-treatment.

By contrast, in the processes described in US. Patent No. 2,739,042 and US. Patent No. 2,948,739, a tetrahydroanthraquinone is extracted from the working solution prior to the dehydrogenation. Needless to say that the extracted tetrahydroanthraquinone can successfully be dehydrogenated in the process of the present invention.

In accordance with the present invention, the dehydrogenation of a tetrahydroanthraquinone is accomplished with a conversion of and a quantitative total anthraquinone recovery is obtained whether a tetrahydroanthraquinone alone or a mixture of a tetrahydroanthraquinone and an anthraquinone is submitted to the dehydrogenation, and further irrespective of the concentration of the tetrahydroanthraquinone or of the kind of the substituent alkyl radicals on the tetrahydroanthraquinone.

The solvents which are applicable to the process of the present invention include aliphatic or aromatic hydrocarbons, alcohols, ketones, esters and any other solvents, which are stable tousual hydrogenation catalysts.

Concerning the reaction temperature, the dehydrogenation proceeds with a fair velocity at a temperature around 100 C., in general with a sufficient velocity at the boiling point of the solvent employed. The dehydrogenation is completed in 2 hours at a temperature between C. and C., while the boiling points of the solvents generally employed in the anthraquinone process fall within the range of 150-200 C.

The dehydrogenation velocity becomes about twice as high by 10 C. elevation of the reaction temperature. Though the reaction temperature is limited by the thermal stability of tetrahydroanthraquinones, the reaction may be carried out even at a temperature as high as 300 C.

As the dehydrogenation catalyst of the present inven tion, alumina, magnesia, alumina-magnesia in spinel form, active carbon, and a carbonate of a metal selected from Group I and II of the Periodic Table are used. They are eifective in the order of magnesia spinel alumina active carbon carbonate.

As the hydrogenation catalyst, an usual hydrogenation catalyst such as palladium, platinum or nickel is applicable. Palladium is most conveniently employed in the process of the present invention as in general palladium is employed as the hydrogenation catalyst of an anthraquinone to the corresponding hydroanthraquinone in the anthraquinone process.

The amount of palladium suiiicient for the process is about 1% based on the weight of the carrier. The metals employed as hydrogenation catalyst can be used either in the form of a mixture with alumina, magnesia, alumina-magnesia in spinel forrn, active charcoal, or .a carbonate of a metal selected from Group I or II of the Periodic Table, or in the form supported on one of the above mentioned substances. 7 The organic compounds with at least one unsaturated bond, which are applicable to the dehydrogenation process include acetylene, ethylene, propylene, and cyclic olefines, of which ethylene and propylene are most conveniently applied as they are commercially obtainable at moderate prices.

The following examples illustrate the process of this invention. Here the terms are employed in the following meanings.

Conversion THAQ present before dehydrogenation (by mol.) THAQ present after dehydrogenation (by mol.)

THAQ present before dehydrogenation (by mol.)

Conversion to anthraquinone AQ converted from THAQ (in mol.) THAQ present before dehydrogenation (by mol.)

RnMARKs.-THAQ: Tetrahydroanthraquinone; AQ: Anthraquinone.

EXAMPLE 1 In a flask provided a thermometer, a stirrer, a reflux condenser and a gas inlet, were placed 100 parts by volume of the solution which comprises 0.0665 moL/l. tetrahydrobutylanthraquinone and 0.607 moL/l. butylanthraquinone dissolved in the mixture of trimethylbenzene and diisobutylcarbinol in the ratio of 50:50 by volume. To the solution were added parts by Weight of Pd-MgAl O (Pd 2%) as catalyst and the solution was heated at 164-168 C. for 3 hours, leading a stream of ethylene gas under the normal pressure at a flow rate of 750 parts by volume per hour. The total volume of ethylene gas thus passed amounted to as seven times as Cir .4 the quantity theoretically required. 99% conversion to the corresponding anthraquinone was attained with total anthraquinone recovery.

EXAMPLE 2 Results of some experiments are shown in the following tables. In each experiment, a solution containing a tetrahydroanthraquinone or a mixture of tetrahydroanthraquinone and anthraquinone was placed with a dehydrogenation catalyst and stirred. Dehydrogenation reaction was carried out by passing a gas having at least one unsaturated bond a't a specified temperature for a definite reaction time. After the specified reaction time, the solid catalyst was filtered oil and the remaining tetrahydroanthraquinone and the produced authraquinone were polarographically determined to evaluate the conversion and the totalaanthraquinone recovery.

Table 1 shows the influence of reaction temperature and the reaction time on the conversion. From the data in Table 1, it is calculated that the dehydrogenation velocity is about doubled by 10 C. elevation of the reaction temperature.

Table 1 Conversion (percent) at- React-iou time 1 after preheating (hours) l The time of arrival of a specified temperature was assigned with 0 hrs Remarks:

Sample: Amylanthraquinone, 0.607 mol./l.+amyltetrahydroanthraquinone 0.0665 moL/l.

Catalyst: Pd (2%)-Al O .MgO spinel (250-300 mesh), 100 g./l.

Solvent: Trimethylbenzene:

=50250 by volume.

Total anthraquinone recovery: 97-100%.

Gas stream: Ethylene.

diisobutylcarbinol Table 2 Catalyst I'd-A1203 Pd-AlzOa Pd-MgAls- Pd-MgO Pd-C Pd-MgCOs Pd-NaCOa Pd-Caa- Pd-SlOz Pd (Pd 2%) (Pd 2%) O4 (Pd 1%) (Pd 4%) (Pd 4%) Pom (Pd 3%) (without (Pd 2%) (Pd 2%) carrier) Amount of catalyst employed (g./1.) 100 80 100 100 80 100 100 100 50 10.0 Concentration (m0l./l.):

Amylanthraquinone. 0. 607 0. 638 O. 607 O. 607 0. 607 0. 607 0. 607 0. 607 0. 607 0. 607 Tetrahydroamylanthraquinone 0.0665 0. 0742 0. 0665 0.0665 0. 0665 0. 0665 O. 0665 0. 0665 0. 0665 0. 0665 Gas passed in stream.-. NB Ethylene Ethylene Ethylene Ethylene Ethylene Ethylene Ethylene Ethylene Ethylene Reaction temp. 0).. 164-168 164-168 164-168 164-168 164-167 163-165 163-164 164-168 164-16 164-168 Reaction time (hrs) 3.0 1.0 3. 0 3. 0 2. 5 3. O 3.0 3. 0 3.0 3. 0 Conversion (pereeut) 56. 8 70. 8 99.0 99 57. 3 12.0 29. 5 0 0 0 Conversion to anthraquinone (pereent) 39. 2 70.8 99.0 99 53. 4 10. 8 23. 6 0 0 0 Total anthraquinone recovery (percent) 69.0 100.0 100.0 100 95 90 80 Remarks: As solvent a mixture of trimethylbenzene and diisobutylearbinol in the volume ration of 50:50 was used.

Table 3 illusrates the influence of the tetrahydroanthraquinone to anthraquinone ratio and of the kind of solvent employed at the conversion and the total anthraquinone recovery. The data in the table shows that 6 quinone to the corresponding anthraquinone which comprises introducing into a solution of said tetrahydroanthraquinone a hydrogen acceptor selected from the group consisting of acetylene, olefines in gaseous form and the present invention can be carried out practically in- 5 cyclic olefines in gaseous form, in the presence of a dependent of the tetrahydroanthraquinone to anthradehydrogenation catalyst selected from the group conquinone ratio and also of the kind of solvent used. EX- sisting of alumina, magnesia, alumina-magnesia in spinel periments conducted by using ethylen and propylene, form, active carbon, magnesium carbonate, sodium carrespectively, gave substantially the same results. Table bonate and potassium carbonate, together with a hy- 4 shows the results of comparison between Pd, Pt and Ni. drogenation catalyst selected from the group consisting As seen in the table, these metals are not substantially of palladium, platinum and nickel. different from one another in respect of catalytic activity. 2. A process as claimed in claim 1 wherein the tetra- Table 3 Solvent (vol. ratio) TMB TMB TMB-DIBO TMB-DIBo TMB-DIBO TMB-DIBC TMB-DIBC-AP Amylanthraquinone 0. 0914 0. 435 0. 607 0. 355 0. 500 Tetrahydroamylanthraquinone (Concn. (mol./l.) 0. 457 0. 041 0. 0707 0. 0707 0. 0005 0. 355 0. 0038 Amount of catalyst, g./l 129 129 100 100 (The same in gram ratio to tetrahydroamylanthraquinone) (1.0) (11. 0) (1. 0) (2.0) (l. 0) Gas passed in stream Ethylene Propylene Ethylene Ethylene Ethylene Ethylene Ethylene Reaction temp. 0.). 155-100 155-100 155-105 157-150 164-168 158-160 105-168 Reaction time (hrs.) 2. 0 2. 0 3. 0 3.0 3.0 3.0 3.0 Conversion (percent) 99.7 99. 4 80. 5 98. 5 99.0 98.0 95 9-97.3 Conversion to anthraquinone (per- 99. 7 9a. 4 s0. 2 97. 0 99. 0 91. 0 95. e-97. 3

Remarks: 1) TMB, DIBG and AP stand for trlmethylbenzene, dlisobutylcarbinol and acetophenone, respectively.

(Pd 2%) was used in all cases.

Table 4 CMBJYSL' Pd-MgAlzCh Pt-M'gAlaO; Nl-MgAlzO4 Amount of catalyst employed (g./1. 100. 0 80. 0 80 Concentration (Incl/1.):

Amylanthraquinone 0. 607 0. 638 0. 626 Tetrahydroamylanthraquinone 0. 0665 0. 0742 0. 0752 Gas passed in strea Ethylene Ethylene Ethylene Reaction temp. (3,) 164-168 165-168 164468 Reaction time (hrs.)-- 3.0 3. 0 3. 00 Conversion (percent) 99. 0 95. 9 88. 5 Conversion to anthraquinone (percent) 99. 0 95. 9 85. 5 Total anthraquinone recovery (percent) 100. 0 100. 0 96. 3

Remarks: In all cases, a solvent comprising trimethylbenzene and diisobutylcarbinol in the vol. ratio of 50:50 was used.

What we claim is:

1. In a process for the production of hydrogen peroxide, the step for the dehydrogenation of tetrahydroanthra- 2) As catalyst, Pd-MgAhO;

hydroanthraquinone is an alkylated tetrahydroanthra quinone.

3. A process as claimed in claim 1 wherein anthraquinone is contained in said solution at the start of the reaction.

4. The process as claimed in claim 1 wherein the dehydrogenation reaction is efiected at a temperature between and 300 C.

5. The process as claimed in claim 4 wherein the dehydrogenation treatment is elfected at about atmospheric pressure.

6. A process as claimed in claim 1 wherein said hydrogen acceptor is ethylene.

7. A process as claimed in claim 1, wherein said hydrogen acceptor is propylene.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR THE PRODUCTION OF HYDROGEN PEROXIDE, THE STEP FOR THE DEHYDROGENATION OF TETRAHYDROANTHRAQUINONE TO THE CORRESPONDING ANTHRAQUINONE WHIHC COMPRISES INTRODUCING INTO A SOLUTION OF SAID TETRAHYDROANTHRAQUINONE A HYDROGEN ACCEPTOR SELECTED FROM THE GROUP CONSISTING OF ACETYLENE, OLEFINS IN GASEOUS FORM AND CYCLIC OLEFINES IN GASEOUS FORM, IN THE PRESENCE OF A DEHYDROGENATION CATALYST SELECTED FROM THE GROUP CONSISTING OF ALUMINA, MAGNESIA, ALUMINA-MAGNESIA IN SPINEL FORM, ACTIVE CARBON, MAGNESIUM CARBONATE, SODIUM CARBONATE AND POTASSIUM CARBONATE, TOGETHER WITH A HYDROGENTATION CATALYST SELECTED GROUP CONSISTING OF PALLADIUM, PLATINUM AND NICKEL. 